Another approach to decreasing dielectric constants and loss tangents has been to incorporate poly(phenylene ether) particles into curable materials. See, e.g., U.S. Pat. No. 5,087,657 to Qureshi et al., and U.S. Pat. No. 7,655,278 to Endo et al.; and U.S. Patent Application Publication No. US 2014/0005340 A1 of Peters et al. However, the methods of these references have the disadvantage of using relatively high-viscosity uncured materials. And the Qureshi and Endo methods have the further disadvantage of using a relatively broad distribution of poly(phenylene ether) particle sizes, which has been found to reduce the strength of the resulting composites. There remains a need for dielectric materials exhibiting low viscosity in the uncured state, and low dielectric constants and loss tangents in the cured state.